Graphical abstract
Highlights: NiCo2O4 nanostructures are prepared via simple hydrothermal method. Outer shell of TiN is then grown through conformal atomic layer deposition. Electrodes exhibit significantly enhanced rate capability with TiN coating. Solid-state polymer electrolyte is employed to improve cycling stability. Full devices show a stack power density of 58.205 mW cm -3 at 0.061 mWh cm -3 .
AbstractTernary transition metal oxides such as NiCo2O4 show great promise as supercapacitor electrode materials. However, the unsatisfactory rate performance of NiCo2O4 may prove to be a major hurdle to its commercial usage. Herein, we report the development of NiCo2O4@TiN core-shell nanostructures for all-solid-state supercapacitors with significantly enhanced rate capability. We demonstrate that a thin layer of TiN conformally grown by atomic layer deposition (ALD) on NiCo2O4 nanofiber arrays plays a key role in improving their electrical conductivity, mechanical stability, and rate performance. Fabricated using the hybrid NiCo2O4@TiN electrodes, the symmetric all-solid-state supercapacitor exhibited an impressive stack power density of 58.205 mW cm -3 at a stack energy density of 0.061 mWh cm -3 . To the best of our knowledge, these values are the highest of any NiCo2O4-based all-solid-state supercapacitor reported. Additionally, the resulting NiCo2O4@TiN all-solid-state device displayed outstanding cycling stability by retaining 70% of its original capacitance after 20,000 cycles at a high current density of 10 mA cm -2 . These results illustrate the promise of ALD-assisted hybrid NiCo2O4@TiN electrodes for sustainable and integrated energy storage applications.